Butadiene is an intermediate in petrochemical products and demand therefor and value thereof are increasing worldwide. For example, 1,3-butadiene is generally prepared by naphtha cracking, direct butene dehydrogenation, oxidative butene dehydrogenation of generating 1,3-butadiene and water through reaction between butene and oxygen, or the like.
Oxidative butene dehydrogenation is very advantageous in that stable water is generated through this reaction. In addition, since oxidative butene dehydrogenation is an exothermic reaction unlike direct butene dehydrogenation, 1,3-butadiene may be produced in a high yield even at low reaction temperature, compared to direct dehydrogenation. Accordingly, oxidative butene dehydrogenation does not require additional heat supply, thereby being very suitable as a commercial process.
However, when heat generation is excessive, reactants are completely oxidized, whereby a side reaction wherein a large amount of Cox is generated may occur. That is, in the case of a ferrite-based catalyst mainly used as a catalyst for oxidative butene dehydrogenation, heat is excessively generated during reaction, thereby causing a relatively high-temperature hot spot. Here, a hot spot refers to a spot or area, the temperature of which is highest due to exothermic reaction, in a fixed bed type catalyst reactor (see graphs of catalysts of FIGS. 2a and 2b illustrated in FIG. 3, a spot at which the temperature inside a reactor elevated by red heat is highest). In particular, excess heat generated at active sites of a catalyst has been known to cause catalyst damage and side reactions. Such catalyst damage and side reactions consequentially cause decrease in butadiene process efficiency.
Referring to FIG. 2a, a catalyst (corresponding to black spots indicated by a1) is physically mixed with an inert material such as aluminum (Al) balls (indicated by a2) to disperse excess heat by diluting the catalyst. However, it can be confirmed from FIG. 2a that it is difficult to accomplish uniform dispersion and, to effectively control a hot spot of a catalyst layer due to direct exposure of a catalyst (a1) to excess heat.